Bicycles

Paul Skilbeck

Tuesday 20 March 2018

Naked's framebuilder notes on a prototype

This is a candid, insider view to the development of a new frame design. Sam Whittingham, designer and builder at Naked, wanted to experiment with what's extreme for a well-rounded trail bike. This is his first prototype in that line.

Photos courtesy Naked Bicycles and Design

Sam Whittingham: "When we started building hardtails again 12 years ago, designing specifically for technical west coast BC riding, we were really progressive. Already we were doing super-long top tubes, long fronts, short stays. As trends have gone longer, lower, slacker we’ve kept on our path because we felt ahead of the curve. But in recent years it's accelerated to oblivion. We felt a need to do more r&d, so this one takes everything we think is good and then takes it a step further. Most of the numbers are more than I think would be a good idea, but I'll know more after riding it more. Funnily enough a lot of companies in the area, like ChroMag, said it looks normal. It's definitely progressive compared to traditional geometry. Maybe not as progressive as Peter Verdone or Pole Bikes, or Mondraker have done, but it's pushing the limits for us and what we think. I wanted to see what’s extreme for a well-rounded trail bike, not a downhill bike.

Below are Sam's written notes about the bike BEFORE riding it. His notes AFTER riding it are lower down in the page.

Purpose and inspirationThis one is all about pushing the limits. I have been racing and riding all types of Mountain Bikes since the mid eighties and watched geometry evolve from cruiser klunkers, to steep glorified road bikes, to massive huck-to-fail tanks, to the pick-a-wheel-size-and-be-a-dick-about-it battle raging over the last 10 years, to the current march towards "longer, lower, slacker". Over the last few years we have been evolving our classic naked hardtail as well. Every bike we build gets little closer to the forward geometry preached by such advocates as Pole, Mondraker, and Peter Verdone. We have always embraced big wheels, big tires, short stays and long front centre, but we have been conservative in pushing the boundaries. This Mountain bike is built for testing some of those limits, to answer the question: Have we gone too far?At the time of writing Sam hadn't ridden the bike, but it looks like it should work

Favorite featuresThere are a few feature we have refined in our hardtails over the years. The swooped curve TT that flows into the seat-stays not only gives a classic look, but also allows strong bracing of the rear triangle and and natural internal tunnel for brake and shifter lines. In order to run Chainstays as short as 415mm with these massive wheels we choose to use what we affectionately refer to as "Roost" spacing. No, this isn't yet another choice (please don't call it a standard!), the component parts are already there. We use a 177x12mm fatbike rear end with an 83mm DH BB (downhill bottom bracket) width with the single ring flipped to the outside. This gives a perfect chainline, the strongest possible rear wheel bracing, wide bb bearing spacing and shortest possible stays. This isn't for everybody of course. Some riders might place more priority or need on narrower q-factor, more heel clearance or simply not want or need stays that short or tires that big. Cuz custom.There's really a lot going on here. You just have to read the paragraph above...

Material and component choicesThat was easy on this bike. Steel for the frame as it allows for a quick build and if we hate this monster, the investment wasn't huge. Parts are all our proven favourites from Shimano, Industry Nine, 9point8, RaceFace, Maxxis Chris King and Fox.Naked has some regular go-to companies for components

Design challenges or featuresThe extremes are the real feature on this one. Biggest rolling diameter possible. shortest rear stays possible. Longest front-centre that still fits. Longest dropper post available. Shortest normal stem available. Lowest BB height we dare. All of these things individually or as a whole might be a step too far, but we are excited to find out.Some riders might choose a smaller tyre for muddy days

Other notesI have always been obsessed with what makes a bike joyful to ride. It doesn't matter how nice a bike looks, if it doesn't fit or isn't fun, it won't be ridden. We are excited to start tinkering with the limits of our cross and road bikes as well.

AFTER

"It has definitely been a good learning experience and it forced me to confront some old assumptions. The question we were attempting to answer with this bike was "how far is too far?". After riding this beast, all I can think is: I haven't found the end yet. What follows are some initial thoughts on where we are currently in our thinking about modern mountain bike geometry designed for technical all-mountain/trail/enduro/aggressive XC style riding. We built a bike to test that pushed at the boundaries of what we thought was a good idea. We pushed a couple of things too far, but barely, and to be honest I had a feeling that would be the case.

Bottom Bracket Height310mm unsagged or 295 sagged is too low for technical XC/Trail riding. It would be fine for descending only. At least now I have more data on the right range for the amount fork travel, ride terrain, crank length and pedal type.

Rear-Centre410mm is about as short as you would ever want to go and only for shorter riders. The shorter the better for technical riding but you lose some suspension ability. I don't mean frame flex here, I mean the amount and speed of movement you have to absorb with your legs as the rear wheel strikes an obstacle. I think the traditional range of 410-440 is about right depending on rider height.

Head AngleThis is basically unimportant. This obsession with this number has got to stop. It is all about where this lets you get the front wheel placed. This number changes drastically depending on how your fork is set up. On this bike, the head angle varies from about 64.8 to 71 depending on how much travel is used. One thing that can be said is that a hardtail should have a MUCH slacker starting head angle than an equivalent duty full-squish. On a hardtail the head angle is always steepening under compression, where as a full suspension can either steepen or slacken. In most cases a fully tends towards more rear compression and so tends to slacken more during use. I can see pushing head angle out to 61 degrees (unsagged) if needed on a hardtail, but no more than 65 degrees on a fully. After that, you are starting to get too much fork binding on all but the steepest descents.

Front-Centre is KING!This is the big revelation (along with steering axis below). I have always moved front-centre around as a resultant of bike fit, as I put most of my faith in handling characteristics of head angle and trail. No more! We have all been riding mountain bikes that are way to short in the front. I had always assumed that the slack head angles required to move the front wheel out would result in a chopper feel and too much wheel flop. I realize now that as long as the stem length is kept to a minimum, the whel flop virtually disappears. What is left is a very stable feeling bike that demands to pushed harder. A normal front-centre for us was in the 70cm range. Even a few years ago, it was not uncommon to be as low as 65cm. Now, I'm thinking 77-830 is the sweet spot, even in our tight twisty west coast trails. I think the biggest advantage is that you are now balanced on a much longer see-saw, so every bump is felt less and keeps you away from both tipping points a little longer (think: less likely to go over the bars). I thought tight climbs would suck, but this was also easier. The long resulting longer wheelbase obviously is far more stable through chunder. Cornering feels awkward at first. This is because positioning is identical to the bikes I have had for the last 10 years but the front wheel is 10cm further out in front so I have to get used to initiating a turn 10cm sooner. When done properly, you can really load the front wheel and carve hard without the feeling of jack-knife. This is also about steering axis.

Steering AxisNeeds to be as direct as possible. For most mountain bikes this means super short stems. It is not so much the short stem that is important but the resulting hand placement relative to the steering axis. A stem with a 32mm reach on a 780mm bar with normal sweep gets you pretty close to being in line with the steering axis of the front fork. being in front of the steering axis in the old days especially with shorter bars and long stems is what gave us the feeling of wheel flop and the horrible jack-knife scenarios.

Wide barsI think we have already pushed this one too far. I just don't see the mechanical advantage of going past 800 for most people or even 780. I go a bit less than this, but only because my local trails are a bit too tight for super wide.

Steep seat anglesWe haven't really pushed this yet. I can see the advantage on a forward geo bike though to get your body weight more centred between the wheels especially when climbing. I can see effective seat angles of 74-77 becoming a useful range.

Lower barsThe long front-centre gives you so much more stability and less chance of pitching over the bars, you no longer need to have a high hand position. I can see a real return to wide flat bars, with "riser" bar looking dated real fast. Slacker head angles helps lower the bars. It will be interesting to see what people do to keep bars low enough as the forks get longer and longer. Frame design and straight down tubes. I'm so excited from a structural point of view to be returning to straight downtubes. With a long front-centre and slacker head angle, I no longer need to use kinked downtubes for fork crown clearance. This is so much stronger.

30.5" wheelsI don't want to get into a wheel-size debate, but after years of trying everything I am hooked on getting the biggest rolling diameter that still fits into desired geometry parameters. For me this is 29x3" wheels and tires. For most this is actually the biggest thing they would notice riding this bike. For me it is the most normal part as I have been riding 29+ for 6 years now. It feels normal. I actually think a 3-3.1" rear tire and 2.6-2.8 front would be optimum volume on a hardtail. For a full suspension trail machine, 2.6-2.8" front and back would be ideal. Fatter tires don't carve as well in hard cornering and feel a bit more vague, especially if rims are not wide enough. They make up for this in chunder sections and general traction. I don't see any disadvantage to having the biggest rolling diamter you can get away with. This has a similar effect to longer wheelbase when you encounter a bump. It is less abrupt, leading to more conservation of forward momentum. larger wheels don't "turn slower", this is a myth. The turn just needs to be started sooner. Once this becomes second nature, the feeling is the same and you can actually corner harder. Again, this is about diameter, not width.

ROOST spacingWe use a 170/177 wide rear hub spacing and an 83mm front BB standard for our 29+ bikes including this one. this allows for rear-centres as short as 405mm and perfect chainline with a DH crank and flipped ring. The 170/177 rear hub allows for a near zero dish wheel which is as strong as you can get. The wider hub spacing does mean heel clearance issues for some riders. Also, the q-factor is a bit wider than a standard mtb but nothing close to a fat bike. I ride everything from very narrow q-factor track bikes to extreme wide fat bikes and find that from an efficiency point of view there is no measurable difference. I prefer the wider stance on a mountain bike especially while standing climbing and all descending. The old mtb standard needs to be killed with fire along with "boost" which was a half-ass attempt to solve strength and clearance issues. I like the current trend of "super boost" which simply uses the 150/157 DH rear spacing along with a traditional 73mm bb and flipped ring or unflipped on 83mm bb. This makes sense for 27+ and standard 29ers. For 29+, though, you need ROOST.

Dropper postYup, they all fail. They are all expensive. And I won't be without one ever again. From my cold dead hands. The more drop the better. In order to get a drop in the range of 175-200mm it means having more straight seat-tube. I acquired some seat tubes from Peter Verdone which solve this little dilemma quite nicely for shorter riders by putting the bend to the BB shell at the last possible moment, giving lots of post depth to work with.